Marc Jacobs’ ex-boyfriend Lorenzo Martone is splitting with his business partner, Ryan Brown. The two are dissolving their model management agency ARC New York at the end of the year. Both Brown and Martone maintain the break was amicable, but a source said the split came after Brown worked and traveled nonstop to promote his clients, while Martone “was walking red carpets promoting himself.” The battle over who will keep their star clients Alessandra Ambrosio, Irina Shayk and Julie Henderson is still brewing, but sources predict they will join Brown at his new camp. Both recently moved out of ARC’s SoHo offices into temporary spaces.